Safety mechanism for punch presses



P. E. BOYD SAFETY MECHANISM FOR PUNCH PRESSES Filed April 20, 1936 5 Sheets-Sheet l March 15, 1938. P. E. BOYD 2,111,060

SAFETY MECHANISM FOR PUNCH PRESSES Filed April 20, 1936 s Sheets-Sheet 2 llll HHI

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SAFETY MECHANISM FOR PUNCH PRESSES Filv ed April 20, 1936 3 Sheets-Sheet 3 l/YVE/V TOIQ:

Patented Mar. 15, 1938 UNITED STATES PATENT OFFICE 4 Claims.

This invention relates toimprovement in safety appliances adapted for punch presses, and provides a device of this character embodying a certain mechanism that is coordinated with the clutch of the press for the purpose of preventing premature engagement and disengagement of the same, which is due to the corners of the jaws of the clutch head and those of the bull gear being rounded as result of Wear.

As this wearingprocess becomes more severe the rounded corners of the clutch jaws have a tendency to engage the jaws of the bull gear continually when the latter is idling and with a pror nounced clattering or pounding effect, thereby causing a rapid wear and rounding of all corners of both sets of jaws, and to the extent whereby all of the jaws must be removed and replaced with new ones, which requires considerable delay and expense at frequent intervals from this cause.

Also with this difficulty the crank of the press will not be caused to stop precisely at high dead center as it should do when the same is operating correctly. On the contrary the crank will stop approximately from five to fifteen degrees before high dead center is reached. This condition prevailing the crank will have the tendency to, and very frequently does drop to low dead center, simultaneously operating the press .at an unexpected time and without Warning to theoperator, which may result in a serious, accident to him. It is understood that the jaws of both the bull gear and clutch head of punch presses have perfectly sharp edges when they are new, and as these elements are engaged in repeated operations the edges will become rounded thus permitting their premature engagement and disengagement, whereas if said edges are kept from being worn this condition is avoided, and it is the purpose of this invention to prevent the wearing of the clutch jaws and thereby make it impossible for the dangerous accidental tripping of the press and rendering the same decidedly more safe for the operator.

Premature release of the clutchjaws is due to the worn condition of the clutch jaws. When the jaws are new and unworn, they are sharp and remain in engagement until roller reaches a point upon cam M corresponding to high dead center of the press. Torque is transmitted through the clutch until theclutch jaws fully clear each other. With worn jaws however, when the movable jaws are retracted to a point such that the worn ends of the jaws overlap, there is a component of force tending to cam the movable jaws away from the other jaws before roller 0 has reached the point on cam M corresponding to high dead center of the press.

The principal object of this invention is to completely overcome this difiiculty by positively preventing premature disengagement of the press at all times.

Another object of the invention is to improve the device as set forth in United States Patent No. 2,014,758, issued to me September 17, 1935, and to further the development in this particular line of industry.

The invention possesses further advantages, all of which will appear concurrently with the following detailed description, illustrated throughout the accompanying drawings, and more fully pointed out in the sub-joined claims.

With reference to the drawings:

Figure 1 is a reduced partial view of the punch press and as the device will appear thereon; and in this view the jaws of the press are shown with the proper clearance when the bull gear is idling.

Figure 2 is also a reduced partial view of a punch press, and showing the device in the act of releasing the jaws of the clutch, head from those of the bull gear.. 7

Figure 3 is a top plan view of the hanger of the device, and broken in places as indicated.

Figure 4 is an elevation of the hanger pin.

Figure 5 is a part section and front elevation of the bracket and hanger.

Figure 6 is a side elevation of the bracket with a portion thereof broken away as shown.

Figure 7 is a top plan assembly of the complete device.

Figure 8 is a top plan view of the bracket.

Figure 9 is a front elevation of the hanger.

Figures l0, l1, and 12 are greatly enlarged cross sectional views of both sets of jaws of the press, and Figure 10 indicates a worn condition of the jaws; Figure 11 shows the jaws when they are new and unworn, and Figure 12 shows an advanced state of worn jaws, or approximately the usual limit in this respect.

Figure 13 is a reduced elevation of the plunger safety cap.

Figure 14 is a. sectional assembly of the cap taken vertically through the center thereof.

Figure 15 is a top plan view of the safety cap housing.

Figure 16 is a section taken directly upon line lfi-lii of Figure 14; and Figure 17 is a section upon line l'l-I'I of Figure 14.

The invention comprises hanger l of the formation as indicated and is adapted to be detachably secured to frame A of the press by cap screws 2 where shown, and remains permanently in this relation with said frame. f

A bracket is provided, having body 3 and the upper portion of said body being extended therefrom and forming neck 4 with transversely extending aperture 5 therethrough, and said bracket is adapted to be pivotally secured to hanger l by means of pin 6 with said aperture and the usual cotter pins therefor. Apertures in hanger l are provided to accommodate pin 6.

Extended from neck 4 is enlargement 1 having vertical passage 8 therethrough for accommodating plunger B, also enlarged vertical passage 9 through lower enlargement Ifl of the bracket for accommodating the lower portion of said shaft.

Referring to Figure 8 hub H is provided and is projected from body I where shown so that lever C may be pivotally secured thereto by cap screw I2.

In Figure 6 elongated recessed portion I3 is provided upon each side of enlargement ill of the bracket so as to clear spring D upon sleeve E and stud F, and referring to Figure 1 it is understood that studs F are adapted to threadedly engage frame A as at G.

The lower end of plunger B has eccentrically mounted roller 0 thereon which is adapted to engage clutch head H, and it is further understood that by virtue of springs D'jaws J of said'head will remain clear of jaws K of bull gear L. When the clutch is tripped for causing engagement, roller 0 is retracted upwardly until it is out of the axial path of cam Mand all parts of the clutch head 1-1. It is understood that after'the operation of the press and cam M returns to normal position as in Figure 1, jaws J and K will be completely disengaged and springs D are provided with a tension adequate so as to overcome springs N, and in this manner it is clearly understood that springs D will "prevent engagement of jaws J of clutch head H. and jaws K of bull gear L, thus positively preventing operation of the press when the same is idling and wear of the clutch jaws. In the construction of punch presses it has always been customary to provide a weight that is mounted upon the top end of plunger B, for obvious reasons, and 'due to the proportion of this weight and being inadequately supported to said plunger, very frequently it breaks off of the plunger and falls to the floor and with grave danger of injuring the pressoperator and "other damage.

In order to completely overcome this difficulty a safety cap arrangement is provided and comprises housing ld which is adapted to be detachably secured to the top surface of enlargement I by cap screws l6 through flange ll of said housing, and it is seen that said flange is adapted to conform substantially to said enlargement. Apertures !8 are provided in flange II for the accommodation of screws I6 as indicated.

Referring more particularly to Figure 14 it is understood that the top end of plunger B is provided with a shoulder as at i9 so as to receive and retain the lower end of spring 29, and the upper end of said spring bears against floating disc 2|. Screw 22 is provided and is adapted to threadedly engage housing 14 where shown, with lock nut 23 as indicated.

The object of spring 2b is to provide the required pressure downwardly upon plunger B to substitute the weight previously explained, and the tension of said spring is effected by screw 22. All parts being inclosed in housing I4 spring is thereby protected in a manner so as to perform its duty accurately at all'times.

Ihe clutch operates in the following manner: Engagement of the clutch is efiected in the ordinary manner by moving roller 0 radially out'of contact with cam M, whereupon springs N thrust the clutch jaws into engagement. Upon the return of roller 0 into the path of cam M, the clutch is disengaged. While torque is being transmitted through clutch jaws J and K, cam M swings the plunger B to the tilted position shown in Figure 2, thereby initially compressing auxiliary springs D. As soon as roller ,0 and cam M effect the disengagement of the clutch jaws, springs D react through roller 0 and cam M tofurther separate the clutch jaws as shown in Figure 1. Thus, when the clutch is disengaged, there is always ample clearance between the clutch jaws and accordeach of said studs having a sleeve with a spring 1 upon the sleeve, means within each of said sides of the enlargement for clearing said springs, comprising an elongated recessed portion.

2. In a safety mechanism for a punch press, a bracket having a vertical body, an extended enlargement upon the upper portion of said bracket and a similar enlargement upon the lower portion thereof, both of said enlargements having 'a vertical p'assage'thereth'rough for the accommodation of the'plunger of the press,-a hub extended upon one side of said bracket and at right angles thereto for accommodating a lever of the trip mechanismofthe' press, and an elongated recessed portion upon each side of aforesaid lower enlargement so as to clear a pair of studs pass- 7 ing through aforesaid body and threadedly engaging the frame of the press, each of said studs having a sleeve and a spring upon said sleeve.

3; In a safety mechanism for a punch press, a hanger and means for securing same to the frame of the press,a bracket and means for pivotally securing the same to said hanger, an enlargement upon the upper portion of said bracket and a similar enlargement upon the lower portion thereof, each of said enlargements having a vertical passage therethrough for the accommodation of the plunger of the press, a hub extended upon one 'side of said bracket and at right angles thereto so as to receive a lever of the trip mechanism of the press; the combination with a pair of studs passing through said bracket and engaging the frame of the press, each of said studs having a sleeve thereon and a spring upon said sleeve, and means upon each side of the 'aforesaid'lower enlargement of said bracket for clearing the springs aforesaid.

4. In a safety mechanism for a punch press having a tiltable bracket and a plunger, a cap for said plunger, said cap comprising a housing and means for detachably securing said housing to aforesaid mechanism directly over said plunger 

